This invention relates to an improved modulated control valve for controlling the flow of combustible gas in an instantaneous water heater.
Increased fuel costs and the need to conserve fuel have changed the manner in which a gas fired instantaneous water heater is used. When gas was inexpensive, the pilot flame, once lighted, would not be turned off, except when some maintenance operations were to be performed, or when the heater would not be used for long intervals of time such as weeks or months. Today gaseous fuel is in short supply and is expensive, and it is desirable to turn off the pilot flame where the water heater will not be used for several hours, or overnight.
Further, improved safety considerations require quicker acting and more reliable and positive operation than has been possible with previously used gas modulating valves in instantaneous water heaters. Fast shut off of gas to the burner when the flow of water through the heater is shut off, also saves fuel.
In some prior gas modulating valves, there was a diaphragm valve controlled by several conditions, such as water flow rate and water temperature, and the extent of opening of which was controlled by differential pressure of the combustible gas. While such valves were quite reliable, they were expensive complex, required external control gas connections, and did not have the speeds of operation now required.
In addition, the pilot flames of prior instantaneous water heater gas valves were difficult and time consuming to light.
The object of the present invention is an improved modulated control valve for controlling the flow of the combustible gas in an instantaneous water heater. The modulated control valve of the present invention provides a system much simpler, economical and reliable than the control valve disclosed in U.S. Pat. No. 4,184,457, which was an improvement of the valve of U.S. Pat. No. 3,917,162, which in turn presented an improvement over the control system disclosed in U.S. Pat. No. 3,806,026, all of which are owned by applicants.